Such roof antennas that are attached to or mounted on a flat surface of the vehicle, particularly a vehicle roof, are known. These roof antennas have a base plate designed as one cast element. Means for receiving and/or sending high-frequency signals, e.g. in the form of circuit boards with electrically conductive structures acting as an antenna or in the form of complete GPS modules, are attached to this base plate. A preferably aerodynamically designed plastic hood is set over these means arranged on the base plate and protects them from exterior influences.
The base plate itself has a threaded stem pointing downward that is cast integral with the base plate and that has a longitudinal slot. For sealing between the base plate and the vehicle roof an elastically moldable rubber-like seal ring can be provided.
A base plate made of one cast material has several disadvantages. On the one hand, large tolerance variations, particularly in the range of several tenths of a millimeter, cannot be avoided so that the installation of the receiving antennas and their sealing is inexact. In addition, such cast material is brittle so that there is some risk that the roof antenna might be damaged during installation when it is fastened to the vehicle roof by means of a threaded stem and a corresponding nut, if this fastening nut is tightened to much. The threaded stem might then break very easily, as the threaded stem generally has a longitudinal slot which makes it fairly fragile. Moreover, as a further disadvantage is to be considered that a certain minimum thickness of the cast base plate is necessary in order to ensure the stability required, which in connection with the material results in an unnecessarily excess weight.